Flash smelting is a pyrometallurgical process in which a finely ground feed material is combusted with a reaction gas. A flash smelting furnace typically includes an elevated reaction shaft at the top of which is positioned a burner where pulverous feed material and reaction gas are brought together. In the case of copper smelting, the feed material is typically ore concentrates containing both copper and iron sulfide minerals. The concentrates are usually mixed with a silica flux and combusted with pre-heated air or oxygen-enriched air. Molten droplets are formed in the reaction shaft and fall to the hearth, forming a copper-rich matte and an iron-rich slag layer. Much of the sulfur in the concentrates combines with oxygen to produce sulfur dioxide which can be exhausted from the furnace as a gas and further treated to produce sulfuric acid.
A conventional burner for a flash smelter includes an injector having a water-cooled sleeve and an internal central lance, a wind box, and a cooling block that integrates with the roof of the furnace reaction shaft. The lower portion of the injection sleeve and the inner edge of the cooling block create an annular channel. The feed material is introduced from above and descends through the injector sleeve into the reaction shaft. Oxygen enriched combustion air enters the wind box and is discharged to the reaction shaft through the annular channel. Deflection of the feed material into the combustion air is promoted by a bell-shaped tip at the lower end of the central lance. In addition, the tip includes multiple perforation jets that direct compressed air outwardly to disperse the feed material in an umbrella-shaped reaction zone. A contoured adjustment ring is mounted slidingly around the lower portion of the injector sleeve within the annular channel. The velocity of the combustion air can be controlled to respond to different flow rates by raising and lowering the adjustment ring with control rods that extend upwardly through the wind box to increase or reduce the cross-sectional flow area in the annular channel. Such a burner for a flash smelting furnace is disclosed in U.S. Pat. No. 6,238,457.
Known burners of this type are associated with disadvantages that can adversely affect their performance. These include failure to achieve maximal mixing of the feed material with the combustion gas to optimize oxygen efficiency within the reactor. In addition, such burners have limited range of velocity control to optimize the performance of the burner relative to the feed material. Known burners are also associated with uneven distribution of feed material through the injector sleeve, which can also adversely affect their performance.
For example, the control rods that raise and lower the adjustment ring can interfere with the even flow of air through the wind box and impede optimal mixing and combustion. It is also difficult to provide water cooling for the adjustment ring, and the ring has a tendency to become sticky or misaligned on the injector sleeve.
In addition, dispersion of feed material by compressed air is less than optimal because the discreet jets used on known lance tips fail to provide a continuous air curtain.
Moreover, known burner designs fail to include means for monitoring how well centered the injector is within the annular channel, or mechanisms for effectively adjusting the injector without having to shut down the furnace.
It is a goal of the inventors to provide an improved burner and burner feed apparatus for a flash smelting furnace that provides better mixing, more optimal oxygen efficiency, improved control, and ease of maintenance.